Where damage has occurred to an internal vessel of the human or animal body such as a blood vessel either by disease or by trauma it is possible to introduce a stent graft to the blood vessel by endoluminal techniques which will restore patency of the blood vessel across the damaged region. Often such damaged regions include side branch vessels. To ensure the blood flow can go into the side branch vessel side branch stent grafts are used.
There can be a problem with such side branch stent grafts that in the region of the bifurcation or exit of a side branch from a main tube disruption to blood flow can occur. This may result in thrombosis occurring which could at least partially block the stent graft. Also, without suitable geometry, blood flowing through such regions may not adequately flow into the side arm or side branch.
It is desired to provide a branched or side arm stent graft which does not compromise blood flow in the main lumen of the stent graft and allows blood flow into the side arm.
Throughout this specification the term distal with respect to a portion of the vasculature, a deployment device or a prosthesis is the end of the vasculature, deployment device or prosthesis further away in the direction of blood flow away from the heart and the term proximal means the portion of the vasculature, deployment device or end of the prosthesis nearer to the heart. When applied to other vessels similar terms such as caudal and cranial should be understood.